MXPA98008717A - Injection molding apparatus having dividing bushings of material fund - Google Patents

Abstract

The present invention relates to a melt splitting bushing having a side surface extending from a trailing end to a leading end for use in a hot channel multiple cavity injection molding apparatus having a plurality of nozzles heated assembled in a molding, for dividing a passage of molten material extending therethrough from an individual inlet to four outlets at the front end thereof, the splitting bushing of molten material comprises at least first, second and third integrally joined layers, the first layer has a back face and a front face, the third layer has a back face, a front face and four separate holes extending therethrough from the back side to the front face, the second face layer has a back face, an anterior face and two separate holes that extend through it from the top After the back face to the front side, the back face of the second layer rests against the front face of the first layer, the front side of the second layer rests against the back side of the third layer, the front side of the first layer and the rear face of the second layer have matching grooves forming a first conduit that branches from the individual inlet to two separate holes extending through the second layer, and the front face of the second layer and the rear face of the second layer. third layer have matching grooves forming two second molten material passages, each of said second molten material passages branching from one of the two separate holes through the second layer to two of the four separate holes extending through the second layer. of the third layer, whereby the passage of molten material extends from the individual inlet through the first molten material conduit, both separate holes through the second layer, the two second conduits of molten material and the four holes separated through the third layer

Description

INJECTION MOLDING APPARATUS THAT HAS DIVIDING BUSHINGS OF CAST MATERIAL BACKGROUND OF THE INVENTION This invention relates generally to multi-layer injection molding apparatuses and more particularly to apparatuses having multiple layer casting bushing seats seated in the molten material distribution manifold for dividing the molten material flowing to annular channels of material melted in the heated nozzles. The injection molding apparatus for making multi-layer protective containers for food or preforms for beverage bottles is well known. Often the inner and outer layers are made of a polyethylene terephthalate (PET) type material with one or more barrier layers made of an ethylene-vinyl alcohol copolymer (EVOH) or nylon type material. In some multi-cavity apparatuses, the two different molten materials are distributed through a single melt distribution manifold having different passages, but preferably for materials such as those having different injection temperatures of almost 296.1 ° C and 204.4 ° C respectively, the two molten materials are distributed through two different melt distribution manifolds. In some cases, the molten materials are injected sequentially, while in other cases sequential injection and co-injection are used. The two materials are injected through a heated nozzle having a central channel of molten material and one or more annular channels of molten material that extend around the central channel of molten material to an inlet leading to the cavity. It is also known to divide the flow of molten material into the annular channel of molten material to provide a more even distribution around the annular channel of molten material. As seen in the patent E.U.A. No. 5,094,603 of the applicants that was issued on March 10, 1992, this has been done by providing a single layer cast material distribution plate mounted between the rear end of the heated nozzles and the front face of the material distribution manifold molten. Although this is suitable for many situations, it has the disadvantage of requiring extensive machining of the front face of the melt distribution manifold and the rear ends of the heated nozzles. Furthermore, it is not suitable for receiving molten material from two separate manifolds and has the disadvantage of increasing the height of the mold.

BRIEF DESCRIPTION OF THE INVENTION Accordingly, it is an object of the present invention to overcome at least partially the disadvantages of the prior art by providing a multi-layer injection molding apparatus having the molten material flowing to an annular channel in the heated nozzles divided into bushing. division of molten material of multiple integral layers seated in the distribution manifold of molten material. Up to this point, in one of its aspects, the invention provides a split bushing of molten material having a side surface extending from a rear end to a front end. The molten material split bushing is used in a hot runner multiple cavity injection molding apparatus having a plurality of heated nozzles mounted in a mold, to divide a passage of molten material extending therethrough from a mold. single entry to four exits at its previous end. The molten material division bushing consists of at least first, second and third layers integrally joined. The first layer has a back face and a front face. The third layer has a back face, a front face and four separate holes extending through it. The second layer has a back face, an anterior face and two spaced holes extending through it. The rear face of the second layer abuts against the front face of the first layer and the front face of the second layer abuts against the rear face of the third layer. The front face of the first layer and the back face of the second layer have matching grooves forming a first molten material conduit which branches from the individual inlet to the two spaced holes extending through the second layer. The front face of the second layer and the rear face of the third layer have matching grooves forming two second passages of molten material. Each of the second molten material conduits branches from one of the two holes separated through the second layer to two of the four separate holes extending through the third layer. In this way, the passage of molten material extends from the individual inlet through the first molten material conduit, the two holes separated through the second layer, the two second molten material conduits and the four separate holes through the molten material. the third layer. In another of its aspects, the invention provides a hot-cavity multi-cavity injection molding apparatus for multi-layer molding having at least one molten material distribution manifold with a front face and a plurality of heated nozzles mounted in a mold. Each heated nozzle has a rear end, an anterior end, a central channel of molten material extending therethrough from the rear end to the anterior end, an annular channel of molten material extending around the central channel of material fused to the front end and four separate holes of molten material extending from the trailing end to the annular channel of molten material. A first passage of molten material from a first source of molten material branches into the molten material distribution manifold and extends through the four separate holes and the annular channel of molten material in each heated nozzle to an inlet adjacent the end of the heated nozzle leading to a cavity in the mold. A second passage of molten material from a second source of molten material branches into at least one manifold of distribution of molten material and extends through the central channel of molten material in each heated nozzle to the injection orifice. There are a number of integral three-layer cast material divider bushings each having a trailing end, a leading end, and a central hole extending therethrough from the trailing end to the leading end. Each melt division bushing is seated on the front face of the molten material distribution manifold with its front end resting against the rear end of one of the heated nozzles. The second passage of molten material that comes from the second source of molten material extends through the central hole in each melt splitting bushing to the central channel of molten material that extends through each heated nozzle. Each melt split hub has a first layer at its trailing end, a third layer at its leading end, and a second layer between the first and third layers. The first, second and third layers are integrally joined to form the split bushing of molten material. The first layer has a back face and a front face. The back face rests against the melt distribution manifold. The third layer has a back face, an anterior face, and four holes spaced around the central hole extending through it from the back face to the anterior face. The front face of the third layer is supported against the rear end of the heated nozzle with the central hole of molten material through the splitting bushing of molten material aligned with the central channel of molten material in the heated nozzle and the four separate holes through the third layer aligned with the four separate holes of molten material at the rear end of the heated nozzle. The second layer has a back face, an anterior face and two spaced holes around the central hole of molten material extending therethrough from the rear face to the anterior face. The rear face of the second layer abuts against the front face of the first layer. The front face of the second layer rests against the rear face of the third layer. The front face of the first layer and the rear face of the second layer have matching grooves therein which form a molten material conduit branching from an inlet aligned with the first passage of molten material in the molten material distribution manifold. up to the two separate holes that extend through the second layer. The front face of the second layer and the rear face of the third layer have matching grooves therein which form the two passages of molten material. Each of the molten material conduits branches from one of the two holes through the second layer to two of the four separate holes extending through the third layer. The first passage of molten material coming from the first source of molten material extends through the two holes separated through the second layer and the four holes separated through the third layer of each molten material division bushing and the four separate holes of molten material and the annular channel of molten material through each heated nozzle. In another of its aspects, the invention provides a hot-cavity multiple-cavity injection molding apparatus for multi-layer molding having one or more melt distribution manifolds with a front face and a plurality of heated nozzles mounted in a mold. Each heated nozzle has a rear end, an anterior end, a central channel of molten material extending therethrough from the trailing end to the anterior end, an annular inner channel of molten material extending around the central channel of the molten material. material fused to the front end with at least one hole of molten material extending from the rear end of the heated nozzle to the inner annular channel of molten material. A first passage of molten material that comes from a first source of molten material branches into the molten material distribution manifold and extends through the central channel of molten material in each heated nozzle to an injection orifice adjacent to the front end of the molten material. the heated nozzle leading to a cavity in the mold. A second passage of molten material coming from a second source of molten material branches into the molten material distribution manifold and extends through the molten material bore and the inner annular channel of molten material in each heated nozzle to the orifice of injection. In this alternative embodiment, each heated nozzle has an annular outer channel of molten material extending to the anterior end around the central channel of molten material and the inner annular channel of molten material. Four separate holes of molten material extend from the trailing end to the annular outer channel of molten material. A number of three-layer integral melt division bushings each having a rear end and a front end are seated on the front face of the molten material distribution manifold. The leading end of the melt splitting bushing bears against the rear end of one of the heated nozzles and the second passage of molten material coming from the second source of molten material extends through at least one hole of molten material to the inner annular channel of molten material in each heated nozzle. Each molten material split hub has a first layer at its rear end, a third layer at its front end and a second layer between the first and third layers. The first, second and third layers are integrally joined to form the split bushing of molten material. The first layer has a back face and an anterior face, with the back face resting against at least one manifold of distribution of molten material. The third layer has a rear face, an anterior face, a central hole and four holes spaced around the central hole extending therethrough from its posterior face to its anterior face. The front face of the third layer rests against the rear end of the heated nozzle. The central hole through the third layer is aligned with the central channel of molten material in the heated nozzle and the four holes separated through the third layer aligned with the four separate holes of molten material at the rear end of the heated nozzle . The second layer has a back face, an anterior face, a central hole extending therethrough from the back face to the front face in alignment with the central hole through the third layer, and two spaced holes around the third layer. central hole that extend through it from the back face to the front face. The outer face of the second layer rests against the anterior face of the first layer and the anterior face of the second layer abuts against the posterior face of the third layer, the anterior face of the first layer and the posterior face of the anterior layer. second layer have matching grooves that form a molten material conduit that branches from an outlet aligned with the first passage of molten material in the molten material distribution manifold to the central hole and the two separate holes extending through the molten material. second layer The front side of the second layer and the rear face of the third layer have matching grooves forming two ducts of molten material Each of the molten material ducts branches from one of the two holes through the second plate up to two of the four separate holes that extend through the third layer The first passage of molten material that comes from the first source of mater The molten ial extends through the central hole through the second layer and through the central hole aligned in the third layer and the central channel of aligned molten material extending through each heated nozzle and through the two separate holes to through the second layer and the four holes separated through the third layer of each melt splitting bushing and the four separate holes of molten material and the annular outer channel of molten material through each heated nozzle. In one more aspect, the invention provides a melt-splitting bushing having a side surface extending from a rear end to a front end. The molten material split bushing is used in a hot runner multi-cavity injection molding apparatus having a plurality of heated nozzles mounted in a mold to divide a passage of molten material extending therethrough from an inlet common on its lateral surface to a plurality of exits at its anterior end. The molten material division bushing consists of a back layer and an anterior layer integrally connected. The back layer has a back face, a front face and an outer surface extending from the back face to the front face. A pair of first ducts of molten material extend inward from the common inlet on its lateral surface to two separate inner ends. Two separate holes extend forward from the inner end of the molten material passages to the front face of the rear layer. The previous layer has a back face, an anterior face and four separate holes that extend through it. The back face of the anterior layer rests against the anterior face of the posterior layer. The anterior face of the posterior layer and the posterior face of the anterior layer have matching grooves forming a pair of second conduits of molten material. Each of the second molten material conduits branches from one of the two separate holes from the back layer to two of the four separate holes extending through the previous layer. In this way, the passage of molten material extends from the common entrance through the first ducts of molten material, the two holes separated through the back layer, the two second ducts of molten material and the four holes separated through of the previous layer. In another of its aspects, the invention further provides a method for making a split bushing of molten material having a side surface extending from a rear end to a front end. The melt splitting bushing is used in a hot runner multiple cavity injection molding apparatus having a plurality of nozzles heated in a mold to divide a passage of molten material extending therethrough from an inlet individual on its lateral surface up to four exits on its front end. The method comprises the steps of making first, second and third layers, each layer having a back face and a front face. Two separate holes are drilled a. through the second layer from the back face to the front face. Four separate holes are drilled through the third layer from the back face to the front face. Matching grooves are machined on the front face of the first layer and the back face of the second layer to form a first molten material conduit branching from the individual inlet to the two spaced holes extending through the second layer. The matching grooves are machined on the front side of the second layer and the rear face of the third layer to form two second conduits of molten material. Each of the second molten material conduits branches from one of the two holes separated through the second layer to two of the four separate holes through the third layer. Welding material is then applied to one of the front surfaces of the first layer and the back surface of the second layer and to one of the front surfaces of the second layer and the back surface of the third layer. The first, second and third layers are assembled with the front surface of the first layer resting against the back surface of the second layer and the front surface of the second layer resting against the back surface of the third layer. The assembled layers are heated in a vacuum oven at a predetermined temperature under a partial vacuum according to a predetermined cycle with which the welding material flows between the first, second and third layers and welds them integrally to form the splitting bushing. of molten material. The passage of molten material extends from the individual inlet on the lateral surface through the first molten material conduit, the two holes separated through the second layer, the two second molten material conduits and the four separate holes through the molten material. the third layer up to the four exits at the front end of the molten material division bushing. More objects and advantages of the invention will appear from the following description taken together with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial sectional view of a portion of the multi-layer injection molding apparatus having integral three-layer melt-splitting bushings according to one embodiment of the invention. Figure 2 is an enlarged sectional view of a portion of Figure 1.

Figure 3 is a schematic isometric view showing the three layers of the melt splitting hub seen in Figure 1 before they are integrally joined. Figure 4 is a similar view showing the other faces of the three layers of the same molten material division bushing. Figure 5 is an open isometric view showing the ducts of molten material in the same molten material dividing bushing. Fig. 6 is a partial sectional view of a portion of the multi-layer injection molding apparatus having integral three-layer melt-splitting bushings according to another embodiment of the invention. Figure 7 is an exploded isometric view which shows the three layers of the melt splitting bushing seen in Figure 6 before being integrally joined. Fig. 8 is a similar view showing the other faces of the three layers of the same melt split bushing. Figure 9 is an open isometric view showing the ducts of molten material in the same molten material dividing bushing. Fig. 10 is a partial sectional view of a portion of the multi-layer injection molding apparatus having integral three-layer melt splitting bushings according to a further embodiment of the invention, and Fig. 11 is a view in enlarged section of figure 10 showing a preform having five layers in the cavity. Figure 12 is an exploded isometric view showing the three layers of the melt splitting bushing seen in Figure 10 before being integrally joined. Fig. 13 is a similar view showing the other faces of the three layers of the same melt split bushing. Figure 14 is an open isometric view showing the ducts of molten material in the same molten material division bushing. Figure 15 is an exploded isometric view showing the two layers of a melt splitting bushing according to another embodiment of the invention. Figure 16 is a similar view showing the other faces of the two layers of the same melt-splitting bushing, and Figure 17 is an open isometric view showing the ducts of molten material in the same melt-dividing bushing .

DETAILED DESCRIPTION OF THE INVENTION Reference is first made to Figures 1 and 2 which show a portion of a multiple cavity injection molding apparatus for molding three layer preforms or other products by coinjection molding. A number of heated nozzles 10 are mounted in a mold 12 with their rear ends 14 abutting against the front face 16 of a front steel cast material distribution manifold 18. Although the mold 12 may have a larger number of plates depending on the application, in this case only one nozzle retainer plate 20, a separator plate 22 and a rear plate 24 are secured together by bolts 26, as well as a cavity retainer plate 28 for ease of illustration. The front tip end 30 of each heated nozzle 10 is aligned with an injection orifice 32 extending through an injection orifice insert 34 cooled to a cavity 36. This cavity 36 for making beverage bottle preforms extends between a cavity insert 38 and a mold center 40 in a conventional manner. A passage of molten material 42 extends from an inlet 44 through a multiple cylindrical extension 46 and branches into the molten material distribution front manifold 18 to extend through a molten material division bushing 48 received in a seat 50 on the front face 16 of the front manifold 18 according to the invention, up to each heated nozzle 10. The molten material division bushings 48 are kept in proper alignment by small alignment pins 52 that extend into the front cast material distribution manifold 18. Although only a single heated nozzle 10 is shown for To facilitate the illustration, it should be understood that in a typical configuration there will be many heated nozzles 10 (eg 32, 48 or 64) seated in the mold to receive the molten material through the passage of molten material 42 which will have a more complex configuration than the one shown Each heated nozzle 10 is seated in an aperture 54 in the nozzle retainer plate 20 with its rear ex-arm 14 abutting with the front end 56 of the melt-splitting bushing 48. The heated nozzle 10 is heated by a heating element. integral electric 58 having a terminal 60. A rear collar portion 62 of each heated nozzle 10 is received in a circular locating seat 64 that extends around the opening 54. This provides an insulating air gap 66 between the heated nozzle 10 and the surrounding mold 12 which is cooled by pumping cooling water through cooling conduits 68. In the configuration shown, each heated nozzle 10 has an insert portion 70 which is secured in a seat 72 by a threaded nozzle seal 73. which is screwed into place and forms the front tip end 30 of the heated nozzle 10. The nozzle seal 70 is made of several pieces of steel 74 that fit together to provide an annular channel of molten material 76 that extends around a central channel of molten material 78 to the front tip end 30. The insert portion 70 of the heated nozzle 10 also has an annular insulating air space 79 extending between the central melt channel 78 and the surrounding annular melt channel 76 to provide some thermal separation therebetween. The central channel of molten material 78 extends from the rear end 14 of the heated nozzle 10, while the surrounding annular melt channel 78 extends from four separate holes of molten material 80 that run to the proximal end 14 of the nozzle heated 10. A circle of spaced holes 82 are drilled in the rearward end 14 of the heated nozzle 10 to extend between the central molten material channel 78 and the surrounding spaced molten material holes 80 to provide some thermal separation therebetween. The front melt distribution manifold 18 is heated by an integral electric heating element 84. It is located by a central locator ring 86 and screws 88 that extend inside each heater nozzle 10 to have an insulating air space 90 that it extends between it and the surrounding cooled mold 12. In this embodiment of the invention, another rear steel fused distribution manifold 92 is mounted on the mold 12 by a number of insulating and flexible spacers 94 extending therebetween and the back plate 24 to extend parallel to the front cast material distribution manifold 18. As can be seen, the two manifolds 18, 92 are separated by heat insulating melt transfer bushes 96 placed therebetween. As described in more detail below, the rear melt distribution manifold 92 is heated by an integral electric heating element 98 to a lower operating temperature of the front melt distribution manifold 18, and the air gap 90. provided by thermally insulating molten material transfer bushes 96 between the two multiple 18, 92 provides thermal insulation between them. In this modality, each thermally insulating melt transfer bushing 96 has a rod portion 100 that extends forwardly from a head portion 101 through a hole 102 in the front melt distribution manifold 18 and a central hole 104 in the molten material division bushing 48 and accurately retains the molten material transfer bushing 96 in place. The molten material transfer bushing 96 also has a central hole 106 that extends through the head portion 101 and the rod portion 100 and receives an elongate pin 108 that also extends through the central channel of molten material 78. in the heated nozzle 10. The elongate pin 108 is fixed in place with a head 110 seated on the rear face of the rear melt distribution manifold 92 and a tapered front end 114 adjacent to, and in alignment with, the bore hole. injection 32. In other embodiments, an elongate valve member actuated may be used in place of the fixed pin 108 to provide valve regulation. Another passage of molten material 116 extends from another inlet 118 and branches into the rear casting manifold 92 to extend through a passageway 120 drilled in the head portion 101 of each molten material transfer bushing 96 to a longitudinal slot 122 machined in each fixed pin 108. Each cast material transfer bushing 92 is mounted in suitable alignment by a small pin 124 extending therebetween and the front cast material distribution manifold 18. The fixed pin 108 is similarly maintained in proper alignment by a small pin 126 extending from its head 110 into the surrounding molten material transfer bushing 96. The passage of molten material 116 then extends around the front end 114 of the fixed pin 108 to the injection orifice 32. In another embodiment, the passage of molten material 116 can be extended through s of two diagonal holes to a central hole in the front end 114 of the fixed pin 108.

Reference is now made to Figures 3-5 to describe how each steel melt splitting hub 48 is made by integrally joining a first layer 132 at its rear end 134, a third layer 136 at its front end 56 and a second layer 136. layer 138 between the first and third layers 132, 136. The first layer 132 is made with a rear face 140 that bears against the front melt distribution manifold 18 and a front face 142 that bears against the rear face 144 of the second layer 138. The leading face 142 of the first layer 132 and the back face 144 of the second layer 138 are machined to have matching grooves 146, 148 which join when the three layers are joined together to form a conduit molten material 150 which branches from an inlet 152 aligned with the passageway of fused material 42 to two separate holes 154 that extend through second layer 138. Third layer 136 is made with an anterior face 156 that abuts against the trailing end 14 of one of the heated nozzles 10 and a rear face 158 that leans against the anterior face 160 of the second layer 138. The front face 160 of the second layer 138 and the back face 158 of the third layer 136 are machined so that each has matching curved grooves 162, 164 that join when the three layers are joined together. yes to form two ducts of molten material curved 166. Each curved cast material conduit 166 branches from one of the two holes 154 through the second layer 138 to two of four separate holes 168 extending through the third layer 136, each in alignment with the other. one of the four holes of molten material 80 at the rear end 14 of the heated nozzle 10. A quantity of nickel alloy (not shown) is applied to the back and front or the front faces 144, 160 of the second layer 138. and then the three layers 132, 138, 136 are assembled together. As can be seen, two pins 170 are mounted to extend through the holes 172 through the second layer 138 within the holes 174, 176 in the first and third layers 132, 136 to ensure that all three layers are properly aligned . The three layers 132, 138, 136 have matching center holes 178, 180, 182 which align to form the central hole 104 through the melt-splitting bushing 48. The assembled layers 132, 138, 136 are then loaded into each other. a vacuum oven and gradually heated to a temperature of about 496 ° C which is above the melting temperature of the nickel alloy. As the furnace is heated, it is evacuated to a relatively high vacuum to remove all of the oxygen, and then partially filled with an inert gas such as argon or nitrogen. When the melting point of the nickel alloy is reached, the nickel alloy melts and flows by capillary action between the first layer 132 and the second layer 138 and between the second layer 138 and the third layer 136 for integrally welding all three layers 132, 138, 136 and form an integral melt splitting bushing 48. An alternative procedure is to join the layers 132, 138 and 136 together as described above and then drill the central hole 104 through the split bushing. integral molten material 48. In use, the injection molding system is assembled as shown in Figure 1 and functions to form three-layer preforms or other products as follows. First, the electric current is applied to the heating element 48 in the front melt distribution manifold 18 and the heating elements 58 in the heated nozzles 10 to heat them to an operating temperature of almost 296.1 ° C. The electric current is also applied to the heating element 98 in the rear melt distribution manifold 92 to heat it to an operating temperature of almost 204.4 ° C. The water is supplied to the cooling conduits 68 to cool the mold 12 and the inlet inserts 34. Molten material hot and pressurized is then injected from separate injection cylinders (not shown) into the first and second passages of molten material 42, 116 through inputs 44, 118 according to a predetermined and continuous injection cycle. The molten material injected into the first passage of molten material 42 is a polyethylene terephthalate (PET) type material.

The first passage of molten material 42 extends from the front melt distribution manifold 18 into the molten material conduit 1? 0 which branches into each molten material division bushing 48 from an inlet 152 to the two separate holes. 154 and then through the two curved melt conduits 166 to the four separate holes 168 aligned with the four holes of molten material 80 at the rear end 14 of the heated nozzles 10. This then flows from those four separate holes 80 towards inside the annular channel of molten material 76 to the injection port 32. The molten material injected into the second passage of molten material 116 is a barrier material such as ethylene vinyl copolymer (EVOH) or nylon. The second passage of molten material 116 branches into the rear melt distribution manifold 92 and extends through the aligned passage 120 in each molten material transfer bushing 96 and the aligned longitudinal groove 122 in each fixed pin 108 through from the central hole 106 in the molten material transfer bushing 96, the central hole 104 in the molten material dividing bushing 48 and the central molten material channel 78 in the heated nozzle 10 to the injection hole 32. During each cycle of injection, a predetermined amount of PET is injected through the first passage of molten material 42 and outer layers 184 thereof adhere to each side 186 of the cavity 36. After a short period from the start of the PET injection, a predetermined amount of less viscous barrier material is then injected simultaneously through the second passage of molten material 116 and forms a layer central 188 between the two outer layers 184 of PET. When the cavidade 36 is almost full, the injection pressure of the barrier material is released, which stops its flow and the PET injection is continued to completely fill the cavities 36. The injection pressure of the PET is then released and then of a short cooling period, the mold 12 is opened for ejection. After ejection, the mold 12 is closed and the injection cycle is repeated continuously every 15 to 30 seconds with a frequency that depends on the thickness of the wall and the number and size of the cavities 36 and the exact materials being molded . Reference is now made to Figures 6-9 which show the injection molding apparatus according to another embodiment of the invention for molding three-layer preforms or other products by coinjection molding. Since many of the elements are the same as those described above, not all elements common to both modalities are described and those that are described again have the same reference numbers as above. In this case, each heated nozzle 10 also has an annular outer channel of molten material 190 that extends to the front tip end 30 around the central channel of molten material 78 and the inner channel of annular molten material 76. The PET in the The first passage of molten material is divided into each splitting bushing of molten material 48 and extends through the annular outer channel of molten material 190 as well as the central channel of molten material 78 in each heated nozzle 10 and the barrier material in the second passage of molten material 116 extends through the inner annular channel of molten material 76 having a smaller diameter than in the previous embodiment. Two separate molten material holes 192 extend from the rear end 14 of each heated nozzle 10 to the inner annular channel of molten material 76. In this embodiment, the thermally insulating molten material transfer bushes 96 have a somewhat different shape with insulating air slots 194 on both the rear face 112 and the front face 196. A circular flange 198 on the front face 196 extends around the central hole 106 and is received in a circular seat200 in the front cast material distribution manifold 18 to locate each heat transfer melt transfer bushing 96 is its place. The central hole 106 through each molten material transfer bushing 96 is aligned with the molten material passageway 116 from the downstream melting die manifold 92 and with a molten material hole 202 extending through the front manifold. of distribution of molten material 18. As seen in figures 7 and 8, in this embodiment there is no central hole through the first layer 132 of the melt splitting bushing 48 and the grooves 146, 148 on the front face 142 of the first layer 132 and the rear face 144 of the second layer 138 are machined differently so that the molten material conduit 150 also extends to the central hole 180, 182 through the second and third layers 136, 138 The first layer 132 of the melt splitting bushing 48 has an off center hole 204 extending therethrough from the rear face 140 to the front face 1. 42 in alignment with a hole 206 extending through the second layer 138 from the back face 144 to the front face 160. These holes 204, 206 are aligned with the hole of molten material 202 through the manifold of material distribution front die 18. The third layer 136 of the melt split hub 48 has two spaced holes 208 extending therethrough from the back face 158 to the front face 156 in alignment with the two separate molten material holes 192. at the rear end 14 of the heated nozzle 10 leading to the inner annular channel of molten material 76. The front face 160 of the second layer 138 and the rear face 158 of the third layer 136 have matching grooves 210, 212 which are joined together. when the three layers are joined to form another molten material conduit 214. The additional molten material conduit 214 branches off from the 203 extending hole through the second layer 138 to the two separate holes 208 that extend through the third layer 136. In this way, the second passage of molten material 116 branches into the rear melt distribution manifold 92 and extends forward through the central hole 106 in each molten material bushing 96 and the aligned hole of molten material 202 in the front melt die distribution manifold 18 to the hole 204, 206 in the first and second layer 132, 138 and then split again into the additional molten material conduit 214 to the two separate holes 208 in the third layer 136 which lead to the two separate molten material holes 192, which in turn extend from the rear end 14 of the heated nozzle 10 to the inner annular channel of molten material 76. Although the additional molten material conduit 214 is shown in this embodiment branching out between the second layer 138 and the third layer 136, in other embodiments it is possible to branch in a similar manner between the first layer 132 and the second layer 138. In use, during each cycle, the molding machine, (not shown) injects a small first amount of PET within the cavities 36 through the first passage of molten material 42 which is split in the melt splitting bushing 48 to extend through both central channels of molten material 78 and the annular outer channel of molten material 76. Predetermined amounts of P? T and the barrier material are then co-injected simultaneously through the first and second passages of molten material 42 and 116 to provide the central layer 188 of barrier material between the two outer layers of PET 184. in the cavities 36. When the cavities 36 are almost full, the injection pressure of the barrier material is released which stops its flow, but the PET flow continues until the cavities 36 are completely filled. The injection pressure of the PET is then released and, after a short cooling period, the mold is opened for ejection. After ejection, the mold is closed and the cycle is repeated continuously every few seconds with a frequency that depends on the number and size of the cavities 36 and on the exact materials being molded. Reference is now made to Figures 10-14 which show the injection molding apparatus according to a further embodiment of the invention for molding five-layer preforms or other products that use valve regulation, as many of the elements are the same. than those previously written, not all elements common to all modalities are described and those that are described again have the same reference numbers. In this case, an elongated valve member 216 is reciprocally moved in the central molten material channel 78 in each heated nozzle 10 by a hydraulic actuating mechanism 218 according to a predetermined cycle. The rod portion 100 of each heat insulating melt transfer bushing 96 extending forward through the hole 102 in the front melt distribution manifold 18 extends through an out-of-center hole 220 in the bushing. of splitting of molten material 48. The second passage of molten material 116 extending from the rear melt distribution manifold 92 extends through a hole 222 in the heat transfer melt transfer bushing 96 into a hole aligned 224 extending from the rear end 14 of the heated nozzle 10 to the annular outer channel of molten material 190. The hole 224 in the heated nozzle 10 is surrounded by a circle of spaced holes 226 to provide thermal insulation for the molten material flowing through the passage of molten material 116. As also seen in Figures 12-14, slots coi Nos. 146, 148 of the front face 142 of the first layer 132 and of the rear face 144 of the second layer 138 of each melt splitting bushing 48 are again machined so that the molten material conduit 150 formed when they are attached the two separate holes 134 and the central hole 180 through the second layer 136 to the inlet 152 are connected to each other. Similarly, matching slots 162, 164 on the anterior face 160 of the second layer 138 and the posterior face 158 the third layer 136 is machined to form a pair of curved slots 166, each of which connects with one of the two holes 154 through the second layer 138 to two of the four separate holes 168 through the third layer 136. Each of the four holes 168 through the third layer 136 is aligned with one of the four holes of molten material 80 at the rear end 14 of the heated nozzle 10 to drive the PET to the outer channel. annular of molten material 190. The three layers 132, 138, 136 also have off-center holes 250, 252, 254 which are large enough to receive the rod portion 100 of the molten material transfer bushing 96 and are aligned to forming the hole 220 in alignment with the hole 224 at the rear end 14 of the heated nozzle 10 extending to the inner annular channel of molten material 76. The first layer 132 of each molten material division bushing 48 also has a portion of neck 228 extending rearwardly through an opening 230 in the front melt distribution manifold 18 to the rear manifold 92. The elongated valve member 216 extends through a hole 232 in the manifold of distribution of subsequent molten material 92 through a central aligned hole 234 in the molten material dividing hub 48 into the aligned central channel of molten material 78 in the heated nozzle 10. The elongated valve member 216 has an elongate rear end or head 236 and a front end 238 that it fits into the injection port 32. The rear end 236 is connected to a front piston 240 seated in a cylinder 242 in the rear part or cylinder plate 24. The activation mechanism 218 also includes a rear piston 244 and the two pistons 240, 244 are driven by controlled hydraulic pressure applied through ducts 246 to reciprocally move the valve member 216 between four different positions. Although hydraulic activation mechanisms 218 are shown to simplify the illustration, of course other types of activation mechanisms such as electromechanical mechanisms can be used for other applications. In the first position, the front end 238 of each valve member 216 is retracted only far enough to allow a small amount of PET to flow through the annular outer channel of molten material 190. Then the front end 238 of each member valve 216 is retracted more than one second to also allow the barrier material to flow through the inner annular channel of molten material 76. The barrier material that flows simultaneously with the PET divides the PET into doe outer layers 248. for a short time, the front end 238 of each valve member 216 is retracted to the third position to allow the PET to flow through the central channel of molten material 78 around the valve member 216. This flow of PET through the central channel of molten material 78 divides the flow of barrier material in two and provides a central layer of PET 256 between two layers 258 of material d and barrier. When the cavities 36 are almost full, the front end 238 of each valve member 216 is returned to the first position by closing the PET flow through the central channel of molten material 78 and the flow of barrier material through the inner channel. annular of molten material 76. The flow of PET through the outer channel of molten material 190 continues until the cavities 36 are completely filled and the valve member 216 is then driven to the closed forward position shown in Fig. 11 in the that its front end 238 is seated in the injection port 32. After a short cooling period, the mold is opened for ejection. After ejection, the mold is closed and the cycle is repeated continuously every 15 to 30 seconds with a frequency that depends on the thickness of the wall and the number and size of cavities 36 and the exact materials that are being molded. Reference is now made to FIGS. 15 to 17 which show a melt splitting bushing 48 suitable for use in an injection molding system such as that shown in FIG. 1. In this embodiment, the material division bushing melted 48 has a back layer 260 and a front layer 262 that are integrally joined together instead of the three layers. The back layer 260 has a back face 264 which forms the rear end 134 of the melt splitting bushing 48, a front face 266 and a cylindrical outer surface 268 extending from the rear face 264 to the front face 266. The layer front 262 also has a rear face 270 and a front face 272 that form the front end of the melt splitting bushing 48. As can be seen, the rear layer 260 has a pair of first passages of molten material 274 extending inwardly. from a common inlet 276 on its outer surface 268. The first molten material conduit 274 extends inwardly to two inner ends 278 which are spaced apart to join two perforated holes 280 extending therefrom to the anterior face 266 of the layer. rear 260. The front face 266 of the back layer 260 and the back face 270 of the front face 262 are machined to have each one n pair of matching grooves 282, 284 that join when the two layers are joined together to form a pair of second curved fused material ducts 286. Each of the second fused material ducts 286 branches from one of the two holes 280 through the back layer 260 to two of four separate holes 238 that extend through the front layer 262. In this embodiment, the anterior and anterior layers 260, 262 also have matching center holes 290, 292 extending therethrough. After the two layers 260, 262 are integrally welded together as described above, the melt splitting bushing 48 is mounted in place with the central holes 290, 292 and the four holes 288 through the front layer 262 aligned respectively with the central channel of molten material 78 and the four holes of molten material 80 at the rear end 14 of the heated nozzle 10. The operation of this mode is the same as that described above and does not need to be repeated. Although the description of the multi-layer injection molding apparatus having integral multi-layer melt splitting bushings has been given with respect to the preferred embodiments, it will be apparent that various modifications are possible without departing from the scope of the invention and understood for those skilled in the art as defined in the following claims. For example, in another embodiment of the invention, the control of the injection orifice by sprue can be used to mold five-layer preforms or other products. In addition, other materials with suitable characteristics can be used instead of PET, EVOH and nylon.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

Claims (19)

NOVELTY OF THE INVENTION CLAIMS

1. A molten material split bushing having a side surface extending from a rear end to a front end for use in a hot runner multiple cavity injection molding apparatus having a plurality of heated nozzles mounted in a mold , for dividing a passage of molten material extending therethrough from an individual inlet to four eals at the front end thereof, the splitting bushing of molten material comprises at least first, second and third integrally bonded layers, the first layer has a back face and a front face, the third layer has a back face, a front face and four separate holes extending therethrough from the back face to the front side, the second layer has a back face , one front face and two separate holes extending through it from the back face to the front face r, the rear face of the second layer is supported against the front face of the first layer, the front face of the second layer is supported against the rear face of the third layer, the front face of the first layer and the face of the second layer. the second layer has matching grooves forming a first conduit that branches from the individual inlet to two separate holes extending through the second layer, and the front face of the second layer and the rear face of the third layer have grooves coinciding that two second conduits of molten material form, each of said second conduits of molten material branches from one of the two holes separated through the second layer to two of the four separate holes extending through the third layer , whereby the passage of molten material extends from the individual inlet through the first molten material conduit, the two holes separated through the second layer, the two second conduits of molten material and the four holes separated through the third layer.

2. A molten material division bushing as claimed in claim 1, further characterized in that it has the first, second and third layers wherein the front face of the third layer is the front end of the molten material division bushing and the four separate holes extending through the third layer each extend to one of the outlets at the front end of the molten material division bushing.

3. A molten material division bushing as claimed in claim 1, further characterized in that the individual inlet is on the side surface of the molten material division bushing.

4. - A melt division bushing as claimed in claim 1, further characterized in that it has a central hole extending therethrough from the rear end to the front end, whereby the two holes through the second layer and the four holes through the third layer are spaced around the central hole.

5. In a multi-layer hot-cavity injection molding apparatus for multi-layer molding having at least one manifold for distributing molten material with a front face and a plurality of heated nozzles mounted in a mold, each nozzle heated has a rear end, a front end, a central channel of molten material extending therethrough from the rear end to the front end, an annular channel of molten material extending around the central channel of molten material to the front end and four separate holes of molten material extending from the trailing end to the annular channel of molten material, whereby a first passage of molten material coming from a first source of molten material branches into at least one manifold of distribution of molten material and extends through four separate molten material holes and the annular channel of molten material in each heated nozzle to an injection hole adjacent to the front end of the heated nozzle leading to a cavity in the mold, and a second passage of molten material coming from a second source of molten material branches into at least one manifold of molten material distribution and extends through the central channel of molten material in each heated nozzle to the injection orifice, the improvement that also includes; a plurality of three-layer integral melt division hubs each having a rear end, a leading end, and a central hole extending therethrough from the trailing end to the leading end, each splitting bushing Molten material is seated on the front face of the molten material distribution manifold with the leading end of the molten material splitting bushing resting against the rear end of one of the heated nozzles and the second part of molten material coming from the second source of molten material extending through the central hole in each molten material division bushing to the central channel of molten material that extends through each heated nozzle, each molten material division bushing has a first layer in the molten material rear end, a third layer at the front end, and a second layer between the first and third layers, the first Mere, second and third layers are integrally joined to one another to form the splitting bushing of molten material, the first layer has a rear face and one front face, the rear face abuts against at least one cast material distribution manifold, the third layer has a rear face, an anterior face, and four holes extending around the central hole extending therethrough from the rear face haeta the anterior face, the anterior face of the third layer abuts against the posterior end of the heated nozzle with the central hole of molten material through the molten material division bushing aligned with the central channel of molten material in the heated nozzle and the four holes separated through the third layer aligned with the four separate holes of material fused at the rear end of the heated nozzle, the second layer has a rear face, an anterior face, and two holes It extends around the central hole of molten material which extends therethrough from the rear face to the front face, the rear face of the second layer abuts against the front face of the first layer, the front face of the second layer. The layer is supported against the rear face of the third layer, the front face of the first layer and the rear face of the second layer have matching grooves forming a distribution conduit branching from an inlet aligned with the first passage of molten material in at least one melt distribution manifold up to the two separate holes extending through the second layer, and the front face of the second layer and the rear face of the third layer have matching grooves forming two material passages fused, each of said conduits of molten material are branched from one of the two holes through the second layer to the doe of the four holes. Eeparadoe extending through the third layer, whereby the first passage of molten material from the first source of molten material extends through two separate holes through the second layer and the four holes separate through of the third layer of each casting bushing of molten material and the four separate holes of molten material and the annular channel of molten material through each heated nozzle.

6. An injection molding apparatus as claimed in claim 5, further characterized in that the first passage of molten material that comes from the first source of molten material branches into a manifold of The distribution of the molten front material mounted on the mold and the second passage of molten material coming from the second source of molten material is branched into a manifold of distribution of molten back material mounted on the mold and then extends through holes in the mold. material 20 melted in the diecast manifold of the front melt material aligned with the central hole of molten material which extends through each of the molten material division bushings. 7.- An injection molding apparatus such as 25 claimed in claim 6, further characterized in that the second passage of molten material extends through holes in molten material transfer separators mounted between the multiples of dietribution of molten material. 8. An injection molding apparatus as claimed in claim 7, further characterized in that an elongated pin extends centrally through the central hole in each melt splitting bushing, and the central channel of molten material in the heated nozzle aligned with the second passage of molten material that comes from the second source of molten material extends around the elongated pin. 9. An injection molding apparatus as claimed in claim 8, further characterized in that the elongated pin is a fixed pin with a groove of molten material extending longitudinally thereon. 10. An injection molding apparatus as claimed in claim 8, further characterized in that the elongated pin is a valve member and further includes an activation mechanism for reciprocally moving the valve member between a retracted open position and a closed front position. 11. In a multi-layered hot-runner multiple-cavity injection molding apparatus having at least one melt distribution manifold with a front face and a plurality of heated nozzles mounted in a mold, each nozzle heated has a rear end, a front end, a central channel of molten material extending therethrough from the trailing end to the front end, an annular inner channel of molten material extending around the central channel of molten material to the front end with at least one hole of molten material extending from the rear end of the heated nozzle to the inner annular channel of molten material, whereby a first passage of molten material coming from a first source of molten material branches out in at least one manifold of distribution of molten material and extends through the central channel of mater ial melted in each heated nozzle to an injection orifice adjacent to the front end of the heated nozzle leading to a cavity in the mold, and a second passage of molten material coming from a second source of molten material branches into at least one multiple distribution of molten material and extends through at least one hole of molten material and the inner annular channel of molten material in each heated nozzle to the injection orifice, the improvement comprising; each heated nozzle has an annular outer channel of molten material extending to the front end around the central channel of molten material and the inner annular channel of molten material, and four separate holes of molten material extending from the rear end to the annular outer channel of molten material, a plurality of three-layer integral melt division bushings each having a rear end and a front end are seated on the front face of the molten material distribution manifold with the front end of the bushing of distribution of molten material leaning against the opposite end of one of the heated nozzle and the second passage of molten material coming from the second source of molten material extending through at least one hole of molten material to the inner annular channel of material melted in each heated nozzle, each melt splitting hub has a first layer at the rear end, a third layer at the front end, and a second layer between the first and third layers, the first, second and third layers are integrally joined together to form the split bushing of molten material, the first layer has a front side and an anterior face, the front face rests against at least one distribution manifold of molten material, the third layer has a rear face, an anterior face, a hole central and four holes spaced around the central hole extending therethrough from the anterior side to the anterior face, the anterior face of the third layer abuts against the posterior end of the mouthpiece heated with the central hole through the third layer aligned with the central channel of molten material in the heated nozzle and the four holes separated through the third layer aligned with the four separate holes of molten material at the rear end of the heated nozzle, the second layer has a rear face, a front face, a central hole extending therethrough from the back face to the front face in alignment with the central hole through the third layer, and two holes spaced around the central hole extending through it from the back face to the front face, the back face of the second layer leans against the front face of the first layer, the front face of the second layer abuts against the rear face of the third layer, the front face of the first layer and the rear face of the second layer have matching grooves therein to form a molten material conduit that is branches from an inlet aligned with the first die of molten material in at least one manifold of molten material distribution to the central hole, and the two holes s eparados that extend through the second layer, and the front face of the second layer and the rear face of the third layer have co-incidental grooves therein that form two passages of molten material, each of said ducts of molten material they branch off from one of the two holes separated through the second layer to two of the four spaced holes that extend through the third layer, thereby making the first passage of molten material that comes from the first source of molten material extends through the central hole through the second layer and through the central hole aligned in the third layer to the aligned central channel of molten material extending through each heated nozzle, and through the open hole through the the second layer and the four holes separated through the third layer of each molten material division bushing to the four holes of material separate fused and annular outer channel of molten material through each heated nozzle. 12. An injection molding apparatus as claimed in claim 11, further characterized in that the first passage of molten material that comes from the first source of molten material branches into a manifold of distribution of molten front material mounted on the mold , and the second passage of molten material that comes from the second source of molten material branches into a manifold of distribution of molten back material mounted on the mold and then extends through hole of molten material into the die manifold of material Frontal melt connected to at least one hole of molten material extending to the inner annular channel of molten material in each heated nozzle. 13. An injection molding apparatus as claimed in claim 12, further characterized in that the second passage of molten material extends through holes of molten material in molten material transfer bushings mounted between the manifold of material distribution molten, the molten material hole being aligned in each molten material transfer bushing with one of the molten material holes in the front molten material distribution manifold. 14. An injection molding apparatus as claimed in claim 13, further characterized in that each heated nozzle has two separate molten holes that extend from the rear end of the inner annular channel of molten material, the third layer of the bushing of splitting of molten material has two other holes spaced around the central hole extending therethrough from the rear face to the front face in alignment with the two separate molten material holes extending from the rear end of the nozzle heated, the first layer of the molten material division bushing has a hole extending through the honeycomb from the rear face to the front face, the second layer of the molten material division bushing has another hole extending through of it from the back face to the front face in alignment with the hole through the prime The layer, the front face of the second layer and the rear face of the third layer also have matching grooves that further form a molten material conduit that branches from the hole through the second layer to the two extending holes that extend through the third aligned layer, whereby the second passage of molten material coming from the second source of molten material extends through the hole of molten material in each molten material transfer bushing, through the aligned hole of the molten material. material melted in the manifold of distribution of front melted material, through the hole aligned in the first layer and the other hole in the second layer and branched in the conduit of additional molten material until the other two holes separated through the third layer to the two separate molten holes that extend from the rear end of the heated nozzle to the inner channel or annular of molten material. 15. An injection molding apparatus as claimed in claim 13, further characterized in that each heated nozzle has two separate holes of molten material extending from the rear end to the inner annular channel of molten material, the second and third The melt splitting bushing layers each have two other spaced holes around the central hole extending therethrough from the rear face to the front face in alignment with the two separate molten material holes extending from the front. At the rear end of the heated nozzle, the first layer of the melt-splitting bushing has a hole extending through the side wall from the rear face to the front face, and the front face of the first layer and the rear face of the rear face. the second layer also have matching grooves that form an additional molten material conduit that branches off from the hole through the first layer to the two separate holes extending through the aligned third layer, whereby the second passage of molten material coming from the second source of molten material extends through the material hole fused into each molten material transfer bushing, through the molten material hole aligned in the front molten material distribution manifold, through the aligned hole in the first layer, and branched into the additional molten material conduit up to two other holes are separated through the second and third layers to the two holes of molten material extending from the rear end of the heated nozzle to the inner annular channel of molten material. 16. An injection molding apparatus as claimed in claim 13, further characterized in that each melt splitting bushing has a molten material bore extending therethrough from the trailing end to the front end, and the second passage of molten material coming from the second molten material source is It extends through holes of molten material in each molten material division bushing to the inner annular channel of molten material in each heated nozzle. 1

7. An injection molding apparatus as claimed in claim 16, further characterized in that the first layer of each melt splitting bushing has a neck portion extending rearwardly through an aperture in the manifold of For the distribution of front molten material, and a valve member hole extends centrally through the first layer of each molten material division bushing, an elongated valve member extends through the valve member hole in the first layer. , the central hole in the second layer, the central hole in the third layer, and the central channel of molten material in the aligned heated nozzle, and the activation mechanism reciprocally moves each elongated valve member between different positions, with that a portion of the first passage of molten material that comes from the first source of molten material extends around the valve member ula elongated. 1

8. A molten material split bushing having a side surface extending from a rear end to a front end for use in a hot runner multilayer injection molding apparatus having a plurality of heated nozzles mounted on a mold for dividing a molten material pad extending through the same of a common entry on the side surface thereof to a plurality of exits on the front end thereof, the molten material split bushing comprises a back layer and an anterior layer integrally joined to each other, the back layer has a back face, a front face, an outer surface extending from the back face to the front face, a pair of first lines of molten material extending inward from the front common socket on the lateral surface thereof to two separate inner ends at a predetermined distance, and Doe separate holes, each hole extends forward from the inner end of one of the molten material passages to the anterior face of the posterior layer, the anterior layer has a posterior face, an anterior face and four separate holes extending to through it from the anterior face haeta the anterior face, the posterior face of the anterior layer is supported against the anterior face of the posterior layer, and the anterior face of the anterior layer and the anterior face of the anterior layer have coincident grooves forming a pair of second fused material ducts, each of the second ducts of molten material branching from one of the two separate holes of the back layer to two of the four separate holes extending through the previous layer, so that the passage of molten material extends from the common entrance through the first molten material conduit, the two holes separated through s of the back layer, the two second conduits of molten material and the four holes separated through the previous layer. 1

9. A method for making a melt splitting bushing having a side surface extending from a trailing end to a leading end for use in a hot channel multiple cavity injection molding apparatus having a plurality of nozzles heated in a mold to divide a passage of molten material that extends through it from an individual entrance on the side surface thereof to four exit at the front end thereof, which comprises the steps of; (a) make first, second and third layers, each layer has a back face and a front face, (b) drill two holes apart through the second layer from the back face to the front face, (c) drill four holes separated through the third layer from the back face to the front face, (d) machining matching slots in the front face of the first layer and the back face of the second layer to form a first pipe of molten material which branches out from the individual entrance to the two separate holes extending through the second layer, (e) machining matching slots on the front face of the second layer and the rear face of the third layer to form two second conduits of molten material, each one of said second conduits of molten material branching from one of the two holes separated through the second layer to two of the four holes separated through the third layer, (f) apply a weld material to at least one anterior surface of the first layer and the back surface of the second layer and to at least one of the anterior surfaces of the second layer and the posterior surface of the third layer, (g) eneamblar the first, second and third layers with the anterior surface of the first layer leaning against the posterior surface of the second layer, and the anterior surface of the second layer leaning against the posterior surface of the third layer, and (h) heating the first layers; , second and third layer assembled in a vacuum oven at a predetermined temperature under a partial vacuum according to a predetermined cycle whereby the welding material flows between the first, second and third layers and integrally welds them to form the bushing. division of molten material so that the passage of molten material extends from the simple entry in the lateral surface through the first conduit of m molten material, the two holes separated through the second layer, the two second channels of molten material and the four holes separated through the third layer until four exit at the front end of the molten material division bushing. SUMMARY OF THE INVENTION A multi-layer injection molding apparatus having integral multi-layer melt-splitting bushings is provided in the melt distribution manifold to divide a first passage of molten material extending to annular channels of molten material into nozzles. heated; matched cast material channels machined on the front face of the first layer and The back face of the second layer of each melt splitting bushing forms a molten material conduit that branches from one inlet to two separate holes extending through the second layer; a pair of matching molten material channels machined on the front face of 15 the second layer and the back face of the third layer of each melt splitting bushing form two conduits of molten material, each of which branches from one of the holes through the second layer to two of four holes separated through the third layer; the four of them 20 holes through the third layer are aligned with four holes of molten material leading to the annular channel of molten material in one of the heated nozzles; a second passage of molten material can be extended through a central hole in each splitting bushing of molten material 25 to a central channel of molten material in the heated nozzle; in another embodiment, the first passage of molten material also extends through central holes in the second and third layers of the melt splitting bushing to a central channel of molten material in the heated nozzle; in this case, the second passage of molten material can be extended through a hole of molten material through the molten-material splitting bushing or can be similarly divided into two in a pipe of molten material extending between two of the Splice bushing layers of molten material. SR / xma * ehp * ram * xal * mmr * P98-1115